That's nonsense and you know it. If you really want to use plain-text web access you can run a local decryption proxy outside of your low-power old computers and use them as if it's 1989.
I actually have no idea what you just said (and you can believe it). But I'll Google "local decryption proxy" and see if that's something feasible I could try with, say, my Powerbook Pismo running macOS 9.2 with no modern browsers. I'm no engineer, so please don't assume everyone here is.
This site is specifically targeted to software engineers, so it's a reasonable assumption that we can talk about the relevant topics without having to simplify things for people outside that group.
For a reverse proxy, you would want a computer capable of the encryption methods the modern web's security standards demand and to install a web server on it which you can access from the older computer. The server computer does not have to be fancy at all. A Raspberry Pi can do it. For software I would recommend either Caddy (https://caddyserver.com/docs/quick-starts/reverse-proxy) or NGINX (https://docs.nginx.com/nginx/admin-guide/web-server/reverse-...). It can be rather complicated and difficult for someone to do, especially if you're not a web programmer.
If both that and upgrading your computer aren't in the cards at the moment, I would think using the recently-discontinued browser Classilla is your best bet: http://www.floodgap.com/software/classilla/ It at least supports some deprecated forms of TLS & SSL. I hear there's a fork called Phoenix that kind of supports TLS 1.2 even.
(I would recommend using the most updated browser regardless.)