[Koha] Securing opac-search

Hello, Koha 24.11.01 Not strictly a Koha problem but something I know a lot of Koha users face. After years of running happily with fail2ban and robots.txt blocking bots/crawlers, the security seems to have passed. We've been getting more and more bots of late switching IPs before bans can take place, perhaps they could be ddos, either way grinding koha to a halt. I've had to switch OPACPublic to disable for now. I can't find much about securing a server against these types of hits. Does anyone else running a small server have any guidance on what could be done/the next steps? I'd ideally like to keep the OPAC public. Thank you Christina