Often I begin from the assumption that the marketplace -- for some reason -- wants to gather as much information about customers as possible, rather than to sell them minimal products that meet their requirements, and so:
- Unless you're careful, searching around may lead you to multiple, spammy-looking websites and domains that appear designed to gather your purchase intent and search information, to share/sell and affect your decision-making
- The products that you find may include surplus functionality (be that hardware, software, subscriptions, tracking, account login requirements, ...) that aren't genuinely required for the requirements that you have
- Since vendors want to build social influence around their products (again, to affect your purchase decision-making and that of your peers), they'll potentially provide rewards, discounts, talking points, and other perks to highly-networked individuals as long as those people remain brand-loyal
- Since continued revenue is an incentive for many vendors, they'll reinvent products on a regular basis and/or use planned obsolescence to encourage you to spend more than once for essentially the same functionality. That could be accompanied by marketing/social-influence campaigns to subtly (or not so subtly) discredit previously-acceptable products (especially if those continue to meet requirements). I can see there being public-good reasons for migration away from problematic products of the past; however I'm not convinced that they're commonly the reason these upgrade cycles are suggested
- If competing products emerge that may meet requirements and are seeing high adoption rates, there is a possibility that vendors will acquire ownership of the competing product outright (stifling competition, although also perversely creating incentives for new-entrant companies to create apparent-competitors that are largely intended to be flipped to a larger incumbent rather than to distribute a lasting higher-quality solution)
- Similarly, if competing products/technologies exist, then vendors may encourage the promotion of brand names that obscure (duplicate, or are similar to) the name of the competitor, causing various forms of confusion and dividing would-be adopters (and their opinions) between the vendor's brand and the competitor's brand
It's possible that I've misinterpreted and misunderstood some behaviours of industry here - based on those, you could be excused for thinking that the goal of these vendors is to extract as much revenue as possible from people as opposed to providing lasting, effective and sustainable products.
By the sounds of it, I think what you want is something like a robust, reliable solid-state music player, as commonly available at low-cost over a decade ago.
The Wirecutter - generally a trustworthy resource - has a section on audio equipment[1], although they don't mention any portable personal music players, as far as I can tell (possibly because many people use their smartphones for this purpose, nowadays).
Rockbox[2] (not to be confused with a similarly-named line of music players) is an open source firmware project that can run on a range of devices[3], many of which may meet most of your requirements.
However, unfortunately it does not appear to have widespread bluetooth support currently. There is work-in-progress[4] on that (last updated in 2020), but one of the challenges with free-and-open-source software is that timescales are difficult to predict, and adding demand/pressure for functionality and bugfixes doesn't always help, so it's hard to tell if-and-when that may be available.
The website gh.de (mentioned in the HN thread that you link to) has a fairly good price-comparison section[5] for portable music players with many relevant filters.
In general: I try to wait until a product that meets requirements arrives (although this often means being well-behind-the-curve compared with peers), try to use the existing devices I have for as long as possible (and extend and enhance their functionality, an area where FOSS can be very helpful), and when possible, purchase products from vendors that have practices aligned with openness, minimalism, high-quality, sustainability and durability. It's difficult! And it leads to frustration after some purchases when realizing that they aren't up to expectations. But that's part of the learning process, too. Good luck.
[1] - https://www.nytimes.com/wirecutter/electronics/audio/
[2] - https://www.rockbox.org/
[3] - https://www.rockbox.org/wiki/TargetStatus
[4] - https://gerrit.rockbox.org/r/c/rockbox/+/3044
[5] - https://geizhals.de/?cat=mmp