1. Move original ssh service to other port, like 2022
2. set gitea config to use port 22
   app.ini

[server]
DISABLE_SSH      = false
SSH_PORT         = 22
SSH_LISTEN_HOST  = 0.0.0.0
SSH_LISTEN_PORT  = 22
START_SSH_SERVER = true

3. execute

sudo setcap CAP_NET_BIND_SERVICE=+eip /usr/local/bin/gitea to enable usage of the port 22