Looking for mailing list manager

Hello,

as i often help non profit organization, i've started to use aliases system for their mails like "Anonaddy" and "SimpleLogin". Overall it's great (preference for Anonaddy because we can send the first email to someone from any alias without having to setup it thru the app first) but they may benefit if they could easily contact a group of people a la Google Groups (not for marketing, but to share informations, unique codes for systems, etc). As those non profits are not in IT, they need tools to be easy to use with their daily apps and hardwares (so mostly webapp with bare minimum management).

• I love listmonk but it looks like a lot to be more marketing intented.
• I wonder if i should go with mailman 3
• I'm questionning PhpList
• Anonaddy would be a good fit but their limitation could cause issue as we have more than 300 members to reach sometime while their support 100 daily contacts in their best plan
• overall something like Google Groups, but self hosted and more privacy friendly

I would like the app to be supported by Softaculous or be available as Docker image.
What's you best bet on that? How you deal with this?

Thanks a lot for your help .