Considerations about replacing my MacBook (2015)

This is for archival purposes only.
A MacBook (2015) was my main rig.
Degradation of MacBook battery. The MacBook is showing some wear after 4 years of heavy use, especially on the battery. Around late 2018, I started to notice reduced capacity in the battery, and the battery icon in the menu bar started shouting "service battery" out of blue. In January 2019, I started monitoring remaining full charge capacity with CoconutBattery every so often. In December 2019, it happened for a couple of times that the battery dies with a remaining charge of 30% or 60%. Similar sudden deaths happened to my previous phone (an iPhone 6, for your information) after 3 years of use. Such incidents warrant a replacement in battery, which would mean a cost of $200. This might not sound awfully too expensive, but it might be avoided if I elect this old MacBook to be my new home server and keep it on its charger all day long.
Is it a good idea to repurpose my MacBook as a home server? Here's a few considerations:
  • ✅ Its low power consumption is ideal for a personal server.
  • ✅ Although deteriorating, the battery can serve as a UPS in case of short power outage. This is some enterprise-level feature an ordinary desktop cannot offer without extra purchase.
  • ❎ I enjoy its portability. If I decided to leave it at home forever, what should I bring with me in case I want to do some computing outside of my room?
    • the next best choice for carrying would be my iPad. Can the iPad serve as a computer? Not if I cannot at least run *nix programs on it. How to make it run *nix programs?
      • ❎ Jailbreak: Some programs requiring x86 CPUs will not work.
      • ❓ Emulator: I'm trying out iSH for this reason.
    • ❓ Can I buy another laptop? An immediate question is WHAT to buy.
      • Another MacBook?
        • ❎ A MacBook or a MacBook Air? Maybe try something else.
        • ❓ A MacBook pro 16'?
          • ✅ Great performance.
          • ✅ Familiar macOS experience.
          • ❎ In terms of portability and (lack of) touchscreen, this device seems a better fit as a home server.
      • A PC laptop? Not until I can feel comfortable using a linux desktop environment!
        • ❓ A Dell XPS 13?
Or would I be better off getting the MacBook battery serviced and -- if I really want to -- buy another computer as a home server?
I'm debating on whether I should buy desktop PC, mainly serving as a home server. Due to mobility requirements, I am looking at tiny-factor machines. Some possible options include:
  • A latest Mac mini with highest configuration ($3,199.00). The tiny factor can be vastly appreciated when I relocate. It occurred to me that re-selling a full-factor desktop PC is not economically ideal, and I will always easily find a monitor and peripherals to plug in a Mac mini wherever I move to. OR: