Each relay only knows the two adjacent clients/servers on a circuit. So the guard sees the client and middle, but not the exit. The middle sees the guard and exit, but not the client. The exit sees the middle and the destination server. A single relay should never be able to link the client to the destination server.
The tor software does not log connections ...
As onion services "live" within the network, you don't need to be an exit to relay onion service traffic.
See https://2019.www.torproject.org/docs/onion-services for details.
Exits are "only" needed for exiting to the clearnet.
Thank you for running any relay.
Tor no longer provides 32-bit armhf versions of tor. You will either need to upgrade your OS to a 64-bit version, build tor from source, or check if Debian provides a compatible 32-bit armhf build. See: https://lists.torproject.org/pipermail/tor-talk/2020-May/045583.html