Mtls requires that the android client device has a certificate installed that matches the one installed on the server in order to access it.

I use https://github.com/dgraziotin/docker-nginx-webdav-nononsense

There are many dockerised fileservers

OMV is quite limiting and maybe a little heavy for the pi(?)

Docker is straightforward Idk what to say You install docker and docker compose on host and run some compose.yml’s to spin up your services

RPI4/400 is perfectly capable as a little home server. All it needs is a good SD card.

Owntracks,photoprism,monocker,brave go m-sync,libre photos,wallabag,radicals e,Baikal,Firefox sync,Joplin web,webdav server,jellyfin,vaultwarden,wireguard