DD-WRT, Tomato, and the like did Great years ago.
As of 3-4 years ago they at best do nothing.
Unless One has some specific need for a feature that does no exsist in the native firmware and can be provided by other firmware, it time to let go and Not act as a "Q-Anon"

version of Enthusiasts.
That is emphatically NOT TRUE, and I am affronted that you would compare the YEARS of DEDICATED 3rd-party development work that goes into those alternative firmwares, with a CRACKPOT CONSPIRACY THEORY PROMULGATED BY MOUTH-BREATHING RETARDS ON FACEBOOK.
Really now, that's a bit over-the-top, and IMHO, quite offensive.
Edit: And to answer your question, the "FreshTomato" fork is still in active development, both MIPS and ARM architecture Broadcom SoC-based hardware. I'm running it right now.
Edit: (insult elided)
Edit: The OP was complaing about his router cutting out, both wireless and wired. Since I started using 3rd-party firmwares, nearly 10-12 years ago, on (*gasp! Refurb!) consumer routers that supported them, I've had literally basically NO TROUBLES, NO NEED TO REBOOT, NO GLITCHES (more or less, there was one refurb Asus AC68U that would drop the 2.4Ghz signal every once in a while), as compared to "factory firmware", that was BUGGY AS HELL.
If for no other reason than GOOD UPTIME, 3rd-party firmware is where it's at. And please, let me know, when "factory firmware" for any of the big makers, implement "encrypted DNSSEC". I'll be waiting.
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TL;DR: Basically, 3rd-party firmwares, use the NEWEST, MOST UP-to-DATE code, that is compatible with the BINARY BLOB DRIVERS that they get from the OEM in the open-source package that they use as the base. Factory firmwares (and you can read this in articles around the web on security of SOHO routers with factory firmware), DO NOT.
3rd-party firmwares, are UPDATED REGULARLY, either on a release schedule, usually quarterly, or bi-monthly. Factory firmwares, often, ARE NOT. (Asus is the exception here, BECAUSE OF AN AGREEMENT WITH THE FTC THAT THEY SUPPORT THEIR ROUTERS WITH SECURITY UPDATES FOR 10 YEARS. Bascially, a "consent decree".)
3rd-party firmwares are generally WIDELY TESTED, and have GREAT UPTIME.
You want newest code. You want regular updates. You want good uptime. --- You WANT 3rd-party firmware.
That's not even touching the interesting new features that they add to the firmware, like DNSSEC and a whole multitude of others, that are not found in factory firmwares, at least not that I've personally seen.