The comments in Does “How will you use this SD card?” wipe data? indicate that the second option in the dialog "Issue with SD card - Tap to fix", which is "Use for portable storage", will also format the external SD card.
My external SD card works without issue from the recovery and I can also mount it after boot from the terminal, but the system does not make it visible e.g. to the file manager app.
I have reinstalled lineageOS recently and until the fourth or so reboot the SD card was working flawlessly and I already used it with the apps that now no longer see it. At the moment, the phone takes long to start with the external SD inserted, and often crashes after unlocking.
How can I avoid reformatting it but still get a behaviour where it works normally and there is no such "issue with SD card" notification?
I have had this issue in the past as well, on different devices, running a different version of (stock) android, with a different SD card. Oftentimes, a reboot or a reinsert of the card would fix it temporarily. But what is going on and how do I actually fix, or at least circumvent, it?