@robw My experience was the opposite. I don't think you need any of the paid Espo stuff - although it is certainly good to support developers. SuiteCRM still looks like a legacy interface, and slow. If you haven't got into Espo Entity Manager, then you're missing out on some rapid capability. Only thing I can see SuiteCRM doing is showing that Espo is faster and easier.
Rocket Chat I don't recommend any more, much prefer Nextcloud Talk.
Open Project is good, but Espo can do everything that OP can.
Phabricator is abandonware.
Jitsi is great, but I think their public service is just fine for most.
UCS is the only free Linux alternative to Active Directory I know of, so useful for that. Clunky though.
Going back to Espo, I paid for all their add-ons but don't really need or use any of them. Get into Entity Manager and you can do everything already with that.
DM me and I'll share a link to what we've done with it. I think you'll see why you couldn't get anywhere near the capability with SuiteCRM.