I don't live in the US, but I've been a traveling tech for all my life, and I've got a few comments:
First paragraph: Here in my country, and I guess all of the EU since these things are usually harmonized, if you're on the clock and you have to leave your work place (which is specified on your contract), not only the company HAS to pay for transportation, but most companies WON'T let you use your own vehicle, so either public transport, a company car or a rental. That is because of the various interpretations of workplace safety regulations.
At my current company, if I leave the "province" (let's say 50km radius from the main city, to simplify) for at least 4 hours, I get paid for a "travelling work" day, a daily extra for each day of work I spend away from the work place. This IS NOT standard, I know many people don't have this on their contract, but it's common for my kind of work.
I have a company card, and every expense has to be registered, it's actually a pain in the ass 'cause I have to both scan every receipt, and also staple them on sheets, detailing the type of expense.
So, in my country (I believe it's the same in the rest of the EU), we have fixed amount of PTO days every year (the amount depends on your contract, but, like pay, it cannot be below 4 weeks), and you HAVE TO USE THEM.
Some people try to build up PTO reserves for whatever reason, and usually their employers have to force them to take time off.
I've been doing HomeLab and HomeLab-adjacent things for over 10 years at this point. My first experience in the space was a Raspberry Pi 2 that I used for a few years to run various services such as Pi-Hole, CUPS, and numerous other software.