I do @MireiaClua 's “Ear Training Workshop” (ETW) exercises on my stationary exercise bike! I use my bike for ~25minutes 4-5 times a week & I have weekly sets of 5 different playlists set up, each having a different set of alternating “Sing The Numbers” (STN) & “Feel The Numbers” (FTN) tracks.
The FTN tracks are part of the ETW course materials and are rather like STN, except that there is no voice, just the backing track plus tones played on keyboard followed by an equal space in which you can sing back the tones as numbers.
Back when I first did the ETW course I would get so totally lost with FTN that I had my playlists as STW only. When I started the second run through I added FTN.
When doing the course run throughs my playlists were oriented to the course week. Now I’ve settled down to a set of 5 which tie into the latter 4 weeks of the course (I split week 10 across two sets, one for ‘the octave’ the other ‘the octave & a half’).
Even now after the second run through the full course, plus a good few months more I’m still far from confident on FTN. I know I’m often wrong. Sometimes I still get totally lost. However, bit by bit I’m improving.
I still don’t think I’m ready for the “Recognising Chords by Ear” follow-up course, but I have hopes that I may feel ready by the time the late January 2021 run of the course comes around? 
2020-09-07: Edit to expand the description of ‘Feel The Numbers’ to mention the ‘sing back’ element.