At least daily, I check the various Slack environments in which I participate. (Actually, since that rose to about eight, it's no longer strictly true).
The best way to contact me is by email, at the address provided above. I ordinarily check email every day.
I can be reached on Signal using my public phone number, and on WhatsApp and Telegram using private numbers.
The phone number is: 07779 296469; callers outside the UK want to try +44 7779 296469.
My phones are gradually being converted to use a virtual phone service I operate myself; more details once it is fully established.
Please don't bother trying to contact me by voicemail or SMS. I try to block all incoming messages via those channels, following repeated problems.
My inbox receives vast amounts of email, sometimes unmanageably so. Here's a chart of its size against time.