The obvious solution that needs more popularity to work:

Obviously there is XMR (or just about any cryptocurrency for that matter). It can be used even in the CLI on very low end hardware assuming you can sync up to a node (not sure this helps plan9 users though).

The pure cash method:

You can typically get paid at a job via either paper check or ACH deposit. With a paper check you could likely cash it almost anywhere, such as a bank or grocery store. With an ACH deposit it goes straight to your bank/credit union. However, you can withdraw this at any time, and similar to XMR (and ie buying it from an exchange), once withdrawn it becomes reasonably anonymous.

You could then pay for things such as utilities at kiosks or in person. Groceries and other items can be bought at brick and mortar stores. Online purchases can be made via giftcards or prepaid debit.

XMR to IRL goods/services:

There also exists reloadable coin cards. While these are in no way anonymous, they do allow for a potentially reusable and continuous solution to converting crypto back into tangible things. I don't know if any are any better than others or have any specific examples to link. You can also buy giftcards with XMR that you can use irl or online (I believe CakeWallet is an example of this).

Fiat to XMR:

Converting fiat into Monero (XMR) is difficult. While the usual recommendations of "checkout Haveno, and look on kycnot.me" still apply, none of the options are great. The most anonymous ones involve putting cash into an envelope and mailing it to someone using a shipping/delivery/postal service. If you are comfortable with this method, go for it I suppose...All the other options are worse for the most part. You could also mine the XMR, if you have a powerful enough computer and unlimited/free electricity, or work and get paid somehow in XMR.

Pseudo-anonyimity:

If your goal is purely pseudo-anonymity, then perhaps checkout something like privacy.com, CloakedWallet or MySudo. Services such as these, that offer "masked" cards, will (if setup appropriately) hide your payments from your bank/bank statement. While this increases your privacy, and might be great for hiding a gift or something from a jointly held account, all that needs to be done is crack open (via either security breach or by legally compelling them, an issues XMR does not have) your, say, privacy.com account and boom an attacker has all the deets. There are some cool features though, relating to security mostly, such as vendor or category locking a card number.

The old style (boomer? luddite?) IRL end-around method:

You could interface with a bank/credit union typically in person or over the phone, thus avoiding their potentially privacy invading app or JS-laden website. However, this strategy relies on them being open during business hours, which is inconvenient at best.

"Online" banking the interoperable way (?):

You could interface with the bank some way, in order to move funds around or similar. Very few open standards regarding this exist (that I am aware), namely OFX (which is a standard) and Plaid (which is a company, but is widely used).

https://infinitekind.tenderapp.com/kb/online-banking-and-bill-pay/direct-connect

MoneyDance is a financial management application that supports Linux. It does not provide a CLI option AIUI. They support both OFX and Plaid (through a subscription service called MoneyDance+). There are other applications that allow you manage one or more financial accounts, however they do not support even Linux TMK.

There's also weboob's "bank" application (weboob is focused on web applications outside of the browser): https://woob.tech/applications/bank However it's somewhat unclear how or if this would actually work.

ATMs exist:

Another (some might consider cheating) would be a kiosk of sorts, or an ATM. Obviously these can be visited wherever present, but fees and compatibility must also be considered. I don't how feasible it is to own or rent an ATM.

Let me know about anything I missed! I've heard the EU has better bank standards and more interoperability. Is this true? What banks or credit unions are "better" for the purposes of this thought experiment? Are there other applications for CLI/interoperable banking? Why not an SSH banking TUI interface?