Ctrl+C works for me. When I use the F command in less, it says "(interrupt to abort)". The "interrupt" that it's referring to is whatever key is bound to the terminal interrupt. The command stty -a shows the relevant terminal settings:

speed 38400 baud; rows 50; columns 80; line = 0; intr = ^C; quit = ^; erase = ^H; kill = ^U; eof = ^D; eol = ; eol2 = ; swtch = ; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0; -parenb -parodd cs8 -hupcl -cstopb cread -clocal -crtscts -ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel -iutf8 opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0 isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke

It's the intr = ^C that shows that interrupt is generated by Ctrl+C.

If you do stty -a what does it show?

Normally CTRL-C is trapped by less so that actually you don't quit from less but rather return to the "standard mode". If you don't like this behavior you can run less with -K option in which case less will exit after CTRL-C. By the way, please note that instead of run less +F file you can just hit F in "normal mode".

So to answer your question: you toggle between modes by pressing F and CTRL-C.

I believe less actually says "Waiting for data... (interrupt to abort)" upon entering this mode, at least when the left-hand side of the pipeline is not producing data fast enough.

"Interrupt" means "Press Ctrl+C". This will send the INT (interrupt) signal to the less process (it sends the signal to all the processes in the foreground process group, which in your case, includes both less and docker-compose).

To avoid sending the interrupt signal to the data-producing command on the left-hand side of the pipeline, you could make that command ignore that signal completely:

( trap '' INT && some-command ) | less

In your case,

( trap '' INT && docker-compose up ) | less