The Orange Pi 5 or Orange Pi 3 LTS are solid options, depending on your budget and how much horsepower you need.

If you don't care about GPIO/serial lines, frankly buy a small NUC or a used Thinkcentre M93p. Used, you can find them for very cheap (£100 in my case), they are powerful enough for your needs, you can have an actual SSD storage, and you will avoid the odd issue with a software not working on ARM (less and less the case but still worth taking into account).

This is slightly different, but in this rpi drought, I've set up proxmox on an old laptop and have several VMs/LXC/containers running on it. It fills that same role for me. I don't know exactly what the power cost comparison is, but it's gotta beat several rpis running simultaneously.

Intel NUC running Ubuntu.

It’s not that difficult to get a Pi 4. I wrote a python script that scraped rpilocator’s rss feed every 5 minutes and would notify my phone when one was available in the US. It went off basically every day around 8:30am PST when Adafruit would drop 100+ Pi4s. I’ve picked up two in the past week (one for my Voron printer and another for a RetroPi cabinet). They did sell out fairly fast.. in about 10 minutes or so.

rock64 works pretty good for my use case as a 700 mbit router.

I've heard good things about the rockpi.

Old laptop or PC. I use an intel NUC for mine. Hosting 30 docker containers

hp t530 or dell wyse 3040 or 5070 thin clients

The OrangePi 5 is one of the better options right now. Starts at $80 for a 4GB (RAM) model and goes all the way up to a 32GB model. CPU is roughly twice as good as an rpi 4, so if you want you can underclock it with no fan and get solid perf still

Lots of cheep SFF/thin client machines on eBay.

I bought a £20 thin client off of eBay to use as a simple file/Emby/pihole and Pivpn server running Ubuntu Server LTS for my home lab

Works great.

The Libre “Le Potato” is nice:

https://libre.computer/products/aml-s905x-cc/

Thin client! They're significantly more powerful than a pi and you can grab them for nothing on eBay and you can use the nvme slots for storage, I've had sd cards go bad in pis

Thin Clients are the way to go! I got a Dell Wyse 5010 for cheap on ebay and replaced the internal 8 GB DOM memory with a 1TB SSD so it's basically a NAS now.

It does take a little DIY (video) but after that it runs more performant than RPis I've had in the past

a cheap second hand laptop will be both faster and will have better wattage and what is basically an internal UPS

Aliexpress has some reasonably affordable fanless mini PCs. Not quite as low power but you can run a heap of containers on them since they are more powerful and x86 and some of them have multiple ethernet ports which can be useful for router purposes etc

Of the alternatives available, Libre Computer, Pine64 and Orange/Banana Pi all offer options that fit what you're looking for. You can generally find these on Amazon, eBay etc at a reasonable price.

I gave up on using raspberry pi for running servers.

I ended up buying a $60 lenovo on ebay https://www.servethehome.com/lenovo-thinkcentre-m710q-tiny-guide-and-ce-review/2/ and then loaded it up with 32GB of ram. Now I run a proxmox hypervisor and around 20+ containers/VMs. Best decision I ever made. I just spin up servers willy nilly

If you don't need GPIO then run a hypervisor. Cheaper than SBCs and more useful.

After running Plex off a pi for like 6 years I think I'm finally about to graduate to a old PC in my closet

Why are rpis hard to find? Are they not making as many anymore?

I have an Odroid c2 for that purpose. Low power but powerful enough to be used for home automation. The c2 is a bit older so there are probably newer versions. https://www.hardkernel.com/

Get a mini pc/NUC with an intel j4125 or better and it will be a great little streaming powerhouse for jellyfin. Usually can grab one for < $150

Lewis from Everything Smart Home dropped a video a few weeks back, telling us about the Zimaboard - https://www.youtube.com/watch?v=jr7vo9NAWfo low power, fanless, single board etc.

I don't need to run amd64 containers, so I like the Orange Pi 5 for raw ARM compute. For $149 you can get one with 16GB of RAM, an NVMe slot and 8 cores, all for < 15 watts.

If you're looking for something to be a disk server, the Odroid HC4 doesn't have as many cores or RAM but it does have 2 SATA slots in a toaster configuration.

Look for secondhand thin clients such as HP T620. They're usually can be had for $30 or less (or more) depending on the configuration. They also have low power usage, not as low as a pi, but still low enough (<10 W).

I'm looking around for a SBC too, under 100$. Can't find stock of banana nor orange Pis. So i forgot about those. I like the features of the odroid boards, and the radxa rock boards. I'll probably buy the rock 4; seems like a good option.