I mean I absolutely don’t use the eMMC, I might as well unsolder it. I use an mSATA SSD and an HDD over USB. It’s full of threads here in the forum on the issue and there’s a very good guide on how to do it Boot from SSD - Outdated description? - #11 by drhm
As for the /srv encrypted problem, it is impossible for me to have it, because every other service (Nextcloud, Syncthing, etc.) starts before the disk is mounted and I have problems with practically everything. I will go back to the standard version of /srv and not put any secrets on the disk.