If that’s the case, I would wait until full disk encryption is usable.
Librem 5 is the one of the few phone that tackling the problem of baseband in an acceptable way. It is a big plus, but not without full disk encryption. The attack vector on baseband is mitm attack of some fake baseband tower, or your data sold by your provider. Both of them required some organization or individuals with sophistication either in terms of technology, finance or power, such as law enforcement, 3 letter agency, some organized crime, or advertisement agency. You are pretty powerless if you are facing former two of them, but it is not likely you as a law-biding citizen being directly targeted, but by immoral use of their power, by chance your detail may be exposed. Same goes to advertisement firm where they gather any personal data as much as all possible source. That’s a worrying concern but not large enough to change a phone since our data are being sold everyday.
However, full disk encryption is different, it’s not about 3 letter agency or advertisement firm, but day-to-day life. For example, if I go to phone repair shop to repair my phone(though I am not sure can a repair shop could repair a Librem phone), without full disk encryption, maybe let say my porn collection with my girlfriend will be exposed to the internet, due to a rogue technician
It is actually happened that some celebrities personal collection is exposed due to rogue technician, and become a scandal.
Another situation is you are forced by law enforcement to hand out your phone. If no full disk encryption in place, your personal data will be exposed in the worst timing during prosecution. Maybe you did nothing wrong, but by trying to prove that you are innocent, you give a device full of personal information which the law enforcement may interpret your data in their own way, which is most likely to be unfavorable to you. You wants to expose those information to a lawyer before law enforcement so that you know what information you should give to law enforcement.
You may say, a encrypted folder is enough, but the thing is you cannot assure. Since there are cache and log files, you may not know cache used by all application in your phone. You could only have a good sleep after losing your phone in someone’s hand if a full disk encryption and the phone being closed after several attempt of password entering.
A new android phone and iphone will have full disk encryption. Though in android, you cannot use different key for locked screen and encryption, which force you to either use a weak key or have an unusable phone. It is possible to bypass this behavior with some hack, but it does not survive an update, which is not really ideal. Ironically, iphone did the best job in terms of disk encryption. Since the disk is encrypted by a passcode, and a different authentication to unlock the screen.
Now, if the first release cannot have a usable full disk encryption, I can wait, but at least don’t repeat the same mistake from android where your encryption key is coupled with the lock screen password. Though I don’t think a normal GNU/Linux has this behavior, but just a reminder if Purism has similar approach on disk encryption with Android.