I had previously been using Home Assistant to try and fix this issue, but after working for a couple of years I was having reliability issues more recently. I also don't have a modbus since I don't want to run a huge ethernet cable to my computer. So I decided to rebuild a custom, lightweight solution for myself using the FoxESS Cloud APIs, and I'm now sharing it for anyone else to use here: https://github.com/ashleydb/octopus-foxess
A simply python script to check for free sessions and cheap rates to set the FoxESS invertor to ForcedCharge (e.g. during intelligent car charging, it will charge the house too), or SelfUse when electricity is expensive. It can notify you via Telegram message, and has a web dashboard too.
Self host this on a PC at home. My setup instructions assume linux, but this is adaptable to Windows too.
Assumes Octopus, Zappi, and FoxESS, but it might inspire someone to adapt for other chargers/inverters too. Or not, and you can keep using your own solution, no biggie.