Before switching ICs became ubiquitous it was common to roll your own with an 8-bit micro. It isn't cost effective now because of the additional external components, board area, and NRE you'd need vs the single chip solution.
I was actually looking into that this week due to chip shortages... it is not cost effective, but if the alternative is sitting and waiting a year for the specialized switch controller to become available again, that NRE doesn't look too bad.