Can only tell you to really consider switching sooner than later. I've used amavis / spamassasin in the past and compared to rspamd, rspamd is a breeze, it's much cleaner in it's configuration and debugging when problems occure.
i will tackle this next year when another server change is coming up. since i have made many changes to spamassassin, the filters should be ported to rspamd if possible.
