i don't have the energy to make a full comic right now, but i do have the energy to type. here's some suggestions i have, with special thanks to the people in the replies of the SP comic for pointing us in the direction of a few of these.
one idea that has been tried and true and will never go out of fashion (anytime soon) is physical journaling. however you go about this is up to you, but it may be good to try keeping dates alongside whatever you choose to write, as this will help you track notable fronts. this can also come with some issues, though, and many of these are solved by:
digital journaling. there are a thousand digital journal services out there, and the most accessible immediately would likely be your notes app. one tool specifically for plurality journaling is lighthouse, which is not shutting down as far as we can see. i'd advise against online tools until the dust has settled, but it's up to you. if you need a good desktop app and don't care if it's plural specific or not, we use rednotebook for diary keeping. it costs very little space or cpu and supports certain features like image embeds. it's just a little buggy on platforms other than linux, which it was natively designed for
mytter and selftalking by shinegori kumagai. a simulated twitter feed and a chatting app, respectively. these apps are good for single purpose, lightweight, android-specific needs. my issues with them, however, are that they run ads, and that they do not have dark modes (that i could find in settings). they're also entirely in japanese UI, although this is less of a barrier than you'd imagine. at most you'd need to tinker for a few minutes. this is what we primarily used to communicate years ago
antar. i have never used antar, but i hear for some people it supports their needs in a chatting app
notion. notion is a powerful general workspace tool that needs a good deal of tlc to turn it into anything useful for system specifics, but if you have experience with it, it seems like a great option
ourcana. similar to simplyplural, entirely offline. no mobile option so far (edit: I've been informed that it does exclusively on its discord)
hivemind. similar to simplyplural, with more features so far. early in development. entirely offline also, but it may not be that way forever. its support and release distribution methods are incredibly unwieldy right now. use this only if you're mostly alright with being your own buoy in the storm
a personal discord server with pluralkit or tupperbox
"okay, but we used sp and octo for the social feature. showing our friends who was fronting and giving them our information!"
do you all use discord? if so, a server with pluralkit or tupperbox and/or a front indicator status could go a very long way
do you all use the same social media? if you use tumblr, you could create an account for your system and give it to friends, which would give them insight into who is fronting at a given time
message signoffs. if you feel the need to do so, you could sign off your messages to your friends, so they're always aware of who they're speaking with
do you see them regularly irl? if so, a physical front indicator of some kind could be very useful. they don't need to be obvious, if you go for discrete options you could sit them down sometime and show them which item means what exactly
you may, for the time, just have to expect your friends to ask you upfront who is around. if this is a legitimate need for you, you wouldn't be selfish or wrong for asking for that level of social accommodation. something to consider
(edit: i forgot to mention because i was exhausted, but pronouns.cc is a great place to house headmate information and it does naturally support plurality in how it operates. you can use it to show pronoun preferences, name preferences, terminology, flags, and write a short bio. it's great)
i hope everyone can find a viable alternative. i'm falling asleep, so i'll stop here. feel free to make many more suggestions in the replies
