Twenty years too late for a "protocol" that is bound to hardware - something we decided was a bad idea forty years ago, and part of why TCP/IP became the standard.
XMPP is a far better protocol, and has had all the features of RCS for 20 years.
Just use the OptiPlex for everything. The RPi lacks the horsepower, and storage capability.
I'm currently using a 7 year old OptiPlex SFF as a NAS, backup point, media converter, and media server. I've upgraded the storage drive to 8TB.
I do have another old NAS I use only to duplicate my data store locally (I keep 3 local copies of data, and a cloud backup).
The OptiPlex draws 15w at idle, about 85w when converting video. My NAS draws about 5w at idle. I initially tried serving media from the NAS, but it's performance is frankly abysmal. Instead I run Media Monkey, Jellyfin, and another media server on the Dell, which has no problem streaming to my crappy Samsung TV (not using an app, just the crappy built-in DLNA client) It works even better with decent devices, like my phone, laptop, iPad.
Your biggest concern with that Dell is the power consumption. As I said, mine happens to draw 15w at idle - I got lucky
What are the specs on your OptiPlex? Is it a mini tower or SFF? That would help more than just telling us the model.
Depending on your sensitivity to failures (drives die) I'd get 2 data drives for the Dell and mirror them, using the current drive just for the OS.
In low-humidity environments, adding moisture to the air can help cool, which is why evaporative coolers work in places like southwest US/arid regions.
When out boating, my friends give me a hard time because I throw on a synthetic long sleeve shirt while on the boat with a real hat.
I went from Verizon ($200/mo for 2 lines) to Xfinity ($80/mo for 2 lines) to JMP.chat ($7/mo for 2 lines) to US Mobile (still about $18/mo for 2 lines). I still have JMP as my cell provider for the SMS-to-XMPP bridge (my sms comes through XMPP), and just have US Mobile for data. My current monthly is still about $20/mo for 2 lines with 10gb of data. Additional data is $4 for 2gig if I go over.
Frankly in the US now US Mobile is hard to beat. Their unlimited plan is $45/mo,and they have coverage on every carrier (my phone will switch to the dominant local carrier wherever I go, and it's usually 5G).
Which means a leak would be "relatively clean" water getting all over the place.
Just doesn't sound like a good idea.
Also, are we talking using this water in chiller cooling towers, like most buildings use? So essentially heating that "relatively clean" liquid to about 100° or so (you know, a temp that microbes just love), and releasing it to the atmosphere.
Also, if you think they're the same, you should study world religions sometime.
Check out courses by The Teaching Company, they cover all major religions (about 20 last I checked.) These are courses as taught in major universities, about 300 level.
Simply put, (and I mean this in a caring way), you're in a growing moment.
Of course you desire physical affection, it's part of human connection. Hell, it could be argued the physical stuff is our primary driver, just like for any other animal, and us humans struggle to reconcile that with our feelings and intellect.
Accept that whatever combo of desires you have (more physical/less personal, or the reverse, or any combo), that's how you feel. It's you, embrace it, and understand it.
As one dating coach put it - "attraction is not a choice". What we do about that attraction is the choice(s) we make.
Sounds like you intellectually get the guy you're currently hooking up with isn't good for you. Then stop seeing him. Seeing him is taking time and energy away from the opportunity to meet someone better for you. It's like spending your time practicing baseball when you want to be a long distance runner.
Two things I can rexommend: read "Your Erroneous Zones" By Wayne Dyer. He shows how to identify mis-thinking, or thinking that's simply not useful, and how to alter our perspective using Cognitive Behavioral Techniques, (without ever calling it that).
Also, check out Evan Marc Katz's dating blog. He's where that quote about attraction came from. You may not agree with some of what he says, but the foundational ideas - know yourself, don't waste your dwindling time with people who aren't good for you, etc, are excellent.
As someone who's (foolishly) also had a couple long-distance relationships - they don't work, because relationships are built through shared experience. You may have time apart once a relationship is well-established, but that's not the same thing as you don't get that day-to-day life sharing. So don't feel bad about it not working out, it would be surprising if it had.
Get a Lenovo Yoga, install the OS of your choice.
I forget the model, but there's a Yoga where the keyboard separates from the screen.
HP also makes a pc tablet (forget the model numbers) with no keyboard - businesses uses them as POS or client-intake systems.
Both if these will blow away any "tablet", as you can run a full OS and use apps of your choice.