Can I upgrade an old MacBook Pro 2015 from Mojave to a newer macOS, and then run a virtualized Mojave in order to keep using iTunes, while also being able to use newer browser versions etc.?
I inquire because I would actually like to do the same – newer versions of the Music app are a usability and visual downgrade. Album view, for example, only shows six fixed-dimension covers, no matter how wide your screen is. Clicking on an album takes you to another screen – annoying! I just want to see the tracklist.
I have a 2018 Macbook that's still running Mojave because I vastly prefer the UI overall. I pray for a UI refresh/patch every WWDC but Apple doesn't really seem to be taking it seriously. Sonoma is an improvement, but there are still so many inconsistent or unpolished areas of the post-Catalina interface style. The cyan-blue folders are still awful; filename selection highlights in Finder aren't centered; the taskbars have become comically large. Small details, but embarrassing for a company of such design pedigree.
Not OP, but I'll give my answer. The unification of different media types in iTunes is a feature, not a bug. (I clung to Retroactive as long as I could; I forget what made me cry uncle.) For actual music, Music.app has been okay, bugs notwithstanding. (I don't use Apple Music, only my local library.)
But the other apps simply aren't as full-featured as iTunes; they align more with Apple's interests as an appliance maker and content vendor (original iTunes preceded the iTunes Store by several years). TV.app preserves some power-user features, like Smart Playlists, while stripping out basics like "Show In Finder". But the one that really grinds my gears is the way audiobooks have been shoe-horned into Books.app, with any semblance of user sovereignty removed.
Example: few years ago, I was planning a road trip, and wanted to quickly filter down a shortlist of audiobooks: "Unread, Genre: Science Fiction, Length < 12 hrs". Not only does the UI offer no affordances for that: it doesn't even display audiobook length, let alone allow sorting by it! I had to dig to find where the files are stored (in `~/Library/Containers`, with gibberish file names), then write a Bash script to `ffprobe` the files and parse the results. When audiobooks were managed by iTunes, this would have been trivial.
I’m running current macOS Sonoma on my MacBook Pro 2015 flawlessly using Open Core Legacy Patcher while presenting to macOS as if I’m running a 15,2 MBP. It’s amazing and has an active dev community and Discord server. I can’t recommend it enough.
Slightly offtopic but for a browser there's Chromium Legacy which is basically Chromium with compatibility patches for older macOS/OS X. Works on 10.8 or higher.
No need to keep Mojave to run iTunes — iTunes can be run on newer macOS, by using Retroactive [1] to patch it.
Regarding running a newer macOS on older hardware, check out OCLP [1] — do make sure you make full backups and have a working recovery plan before trying anything with OCLP though. I know that might sound somewhat obvious to a lot of folk, but you'd be surprised at the amount of folk that jump in and try OCLP on their main system without any backup plan.
Note that are some gotchas re installing OCLP on some older h/w, and it will help to read up on possible issues before wading in. e.g. during installation it might be necessary to use a wired keyboard and mouse, via a USB hub, until the installation is done, you might also need a wired network connection during install, similarly. Depends on h/w (I've not patched MacBooks myself, yet). Once the patcher is done, these should not be needed anymore.
Official support for OCLP is only via Discord — but there is a very active unofficial peer/user support group on FB [3]
I love the MBP 2015. This MacBook model actually supports MacOS Monterey natively. That's three editions newer than Mojave. It just requires an OS reinstall. After you backup your files, you can reboot it while holding ALT+CMD+R to start online recovery mode. That will let you download and install the latest MacOS version the hardware supports.
If so, how would I do this?