@carlosgonz Thank you for your support.
To tell the full story: I have made quite some tries to adjust the “Fritz!Box 7520”, but in the end, none really worked. The router does a lot of tricks. It offers both 2,4 and 5 GHz at the same time. Initially and with the default configuration, it was possible to connect, but not good enough for any download. Additionally, it had to learn about the datetime issue first. After finding that the router’s abilities can be related to the problem, i reduced the protocols level on the router and found, that i additionally have what appears as a range or signal strength issue. It worked in a range of about 1 meter around the router. The connection then became stable enough to upgrade and install a ssh-server.
Matters appeared to be improved also with the kernel you point me to. I could set back the router to its default configuration, but without range improvements.
From both the administration surface of the router as well as from the logs, the “Fritz!Box 7520” simply appears be quite tricky and happily juggles with protocols, channels, signal strength and everything else during operation. I think the L5 tries to follow and negotiate all this with the router, but with a result that leads to what appears as a poor signal strength and still with occasional connection drops.
At that point, i additionally stumbled into the no return from sleep issue and had to reboot the device forcedly for several times leading to the issue in the topic. Well, yes, one can call this a rough start.
The decision to try another router came out right. Contrary to your experience, perhaps because it is a “GL-AR150-Ext” really, the cover is at least 10 m, enough for me. I’ve let the L5 run for a night and don’t see any connection drops in the log now. Operation with the device feels stable now. From that finding, i do think the signal strength problems i experienced with the first router can not be attributed to the L5’s hardware, but rather to some negotiation incompatibility with the Fritz!Box.
As for the linux-image-5.11.0-1-librem5, is do confirm my finding. I’ve reinstalled the kernel with same outcome (i.e. failure of pulseaudio to open the modem sound), so the issue should be replicable. If you want, i can do any test you want to narrow down the problem.
Thanks again, carlosgonz. I for one did not expect that everything runs smooth from the start and that a long list of issues will have to be worked down for a while. I’ll try out some USB-C docks next to get a wired connection, too.