I remember in XP, Vista and 7 using the UXtheme dll mod to get third party themes. First the loss of the sidebar then the drop-off of themers. I skipped 8 and by 10 I’d had enough. Didn’t really come back to theming until I made the jump to full-time Linux in 2022. Theming support being there by default in KDE is amazing. I miss the 2007-2018 themes but Oxygen keeps me happy for now.
Not really. Most recommend Framework because their laptops are open to the point where third parties can make random peripherals that fit the expansion ports. They have a page to help with choosing a distro for their hardware as well. It’s great to see this level of open-ness and repairability in a laptop. Naturally, Linux users gravitate to such a brand.
System76 leverage their own distro, Pop!_OS as a selling point for their laptops, as they have some degree of control over the hardware and software.
The other maker I’d recommend is Tuxedo Computers who also maintain their own distro for hardware they sell.