Hot glue. See Will any pre-existing phone cases work for Librem 5? for a little DIY-video linki 
I agree on the case problem. Fortunetely there is already are stl files available for DIY printing: https://source.puri.sm/Librem-5-Case-Creating-Community/librem-5-model/-/tree/master (I haven’t tested them - yet).
It’s doubtful there could be one that’s as thick as the L5.
But maybe find a match for the height and width, then cut off the back, leaving only a silicone/TPU bumper that would wrap around the L5’s edges and protect the screen somewhat?
In the community-wiki https://source.puri.sm/Librem5/community-wiki/-/wikis/Tested%20Accessories#cases there is listed as 1st item a case which seems to fit, even if it is a bit expensive. But, I couldn’t find a reseller in Europe.
they all appear to be more like sleeves and holsters than just regular cases. Purism could 3D print their own company branded cases and I would buy one in a second, especially if it has a kickstand attached.
Thank you all, so to summarize, we have :
Too bad there is no official silicon case, such a phone is rare. To tell you how important this phone is: I never used silicone protector on my smartphones, but this L5 is different, I’m afraid to break its screen as I did with my current phone.
I found a couple of resources to aid the search for phones with similar dimensions to the L5’s 153mm x 75mm x 15.5mm frame and 5.7-inch/720 x 1440 screen:
https://www.gsmscore.com/model-finder/dimensions/
Goes hand in hand with the concept of user replacable parts. (Like the marketing point of the L5 battery.)
Thank you for sharing those links. Seeing gsmscore website, I’ve found that the Samsung Galaxy J7 2017 has almost the same Height and Width than the Librem 5, so I had the idea to buy a TPU shell for experimental purposes. Not sure if it works or if the final result will be aesthetic, but I have to try!
I also think about the screen replacement. This one is a big concern as I can’t find it in the accessories part of the shop (maybe I missed something such as wrong section of the store).
Anything that you 3D print will shatter or crack the first time stress is applied to it. You need a strong case and display protector. I would look more in to milling something bigger to fit, as opposed to printing. Something slightly bigger might be made to fit using thick (foam embedded) two-sided tape to take up any slack space and/or help hold the phone in to the case if the case is slightly bigger.
Or a belt sander may be easier than milling. Especially if it only adjusting the corners.
Another idea: after separating the back of the case from the sides, use adhesive Velcro squares to attach it to the back of the L5, cutting a hole for the camera and flash, if necessary. 
Hello, thank you for your proposal, I am a bit discouraged but I shall maybe try it. Please find my feedback about my DIY FAIL ^^ :
First of all, the TPU material is very good to make cases : I can feel it can protect the phone. The dimensions (Height & Width) fit exactly on the L5, the thickness… not at all !
After cutting the back side of the case, I could finally put the case around the L5, however :
Conclusion: it is better to print a 3D TPU shell (and ideally that Purism proposes an official shell via a partnership).
My question is: looking at this STL file, I can’t quite figure out if the edges protect the screen by wrapping it slightly or if it’s flat (and therefore not protective). It looks like it does protect the screen, what do you think about it?
Last but not least, do you think it is possible to round the corners a little more to avoid having a too rectangular shape?
Thank you !
Hi, so has anyone found a source you can send these 3d designs to and get something printed? not having ever had anything 3d printed I wonder how hard it is… maybe I will just put my phone in bubble-wrap until I get something figured out LOL
I’m using this fitBag (the 3rd item in this table https://source.puri.sm/Librem5/community-wiki/-/wikis/Tested%20Accessories#cases) and I was since the beginning afraid that the L5 could fall down while pulling it out of the bag or putting it in again. And yesterday it happened. I was able to put my shoe on the point where it would hit the ground and so no damage happened. As a rule of thump I will do it in the future only above a table or above my lap.
A good case should protect the display and the four corners of the L5 and should allow that the heat goes out too.
How big a consideration would heat dissipation be? If the case covered the back, should it have something like a grid of little holes or something to let heat out?
I think more important are holes on the side because the heat gets delivered through the metallic side frames of the L5. This must be tested, though.
So here I am again for a 3D case feedback !
I decided to take this STL file proposed in the gitlab and not having a 3D printer, I sent it to a professional who uses MJF injection technology, and I chose TPU for its flexibility and at the same time robustness properties.
the 3D printing shell made in MJF/TPU is very impressive: no streaks, no burrs, the holes are respected and the angles too. As if it came from a factory. The thickness of the walls gives an impression of great strength, and the rough texture gives a feeling of grip that I particularly appreciate.
Dimensions:
the dimensions are good but not perfect in my opinion. The holes on the sides are such that there is a slight looseness and therefore it does not fit the smartphone 100%. By analogy, to give an idea, let’s say it fits horizontally at 95% without the shell coming off easily. Buttons and switches remain accessible even if you have to make a small effort to reach them (the author of the STL file played on the relief with “chamfers” to facilitate access to the buttons, it’s a good idea), and the USB and audio jack connectors are wide enough to connect cables without being blocked by the shell.
Robustness:
we are not disappointed, the person who made the STL file had the very good idea to cover the relief of the 2.5D screen, which is the most critical part of the device. On several fall scenarios, the shell might protects the smartphone well but there may be scenarios where the screen can break (eg: violently flat, a large part of the shock could be absorbed by the shell, but it may be that the deformation causes a floor-screen contact) and that’s where a glass screen protector can help to absorb the rest of the shock.
Aesthetics:
this is where the real problem lies. I already noticed it a while ago: the corners are almost rectangular, a lot of holes are too, and the thickness makes it look too rectangular and massive in hand / on the table. With this case, we move away from the shape of a smartphone, especially when you stick the device on your cheek to call.
There are definitely areas of improvement for this STL file. I have in mind a few things to improve:
If someone knows an open-source and user-friendly (I am a totally beginner) software to help me to modify this STL file, please do not hesitate. If you are afraid that it will take me years to get the software in hand, you can also start making STL updates following my comments!
Would you mind posting a picture or two?