Well, you have several options. The easiest, and what I would recommend for the time being, is to just stay on Windows 10 for a while longer. Unless you really need Windows 11 for a specific reason, you will be fine on Windows 10, as it still supported through most of next year, possibly longer if MS decides to extend it due to backlash.
If/when you do need to update to Windows 11, the cheapest option would be to make a modified installer so that you could install/upgrade to Windows 11 on your current CPU. Even though it is not officially supported, it would still work, there are ways around the artificial MS limitations.
If you really want to upgrade your CPU, well, it depends on what is available in the future and at what price. I am not certain if your motherboard works with the 5000 series APUs, but at the current time, I would recommend a Ryzen 5600G, if it would work. Now this would likely require a BIOS update for your board, but strangely enough, the 5000 series aren't listed as supported, which is weird, I would think they would be. Maybe this is because this is a "PRO" board. Even though it gets AGESA updates, I do not know if that automatically includes support for the newer CPUs. You may want to do some research on the web to see if anyone has gotten your board to work with a 5600G or similar, or possibly contact MSI for support regarding this.
If there is no hope in getting a 5600G to work, another option would be to source something like a 3400G. At this point it may be best to get one of these used on ebay or the like, as older CPUs are harder to find "new" and these are at inflated prices.