I spent a lot of money on my computer and kept it way too long. Maybe 10 years. I wanted to sell it and got $25 for it. Not even worth shipping!! I then tried to donate it and no one, not even schools would take it. I had to throw it away (recycled). I then wondered how odd it was for me to hold on to the computer for so long so I asked a bunch of people to my shock, I was far and away the oldest computer. No one holds on to their computer so long, they become completely worthless! Better to spend less and upgrade more often then spend a fortune to lock yourself in to a computer that will be worthless. I couldn't upgrade anything either. Nothing was compatible by the time I got rid of it.
I say definitely upgrade to windows or maybe if you've had your computer for 5 or so years, sell it if you can and buy a new computer that has Windows 11.