here's a few perspectives:

zeroth perspective: there are many alternative assets and asset classes for investing your hard-won capital , benchmark any decision against standard alternatives, such as investing in real estate, buying into passive ETFs of the world stock market, buying options of highly-liquid public companies that run at a profit and have years of audited financial reports you can read to help you determine a fair valuation, etc.

if this was a company with a liquid options market, you could sell your options, and with the cash from selling them, consider investing in some new options with a longer expiry time and more attractive strike price -- say +12 months, not 90 days. is anyone willing to buy your options? for what price?

you could attempt to do some discounted cash flow model of the company: e.g. does the company have enough cash and resources to limp along burning cash slowly until its revenue has grown enough to run at a profit? how long might that take under pessimistic or optimistic assumptions about revenue growth? this analysis would be hugely speculative and sensitive to assumptions, but might help you come to a conclusion. to make the analysis simpler you could assume that you own 100% of the company and there are no other shareholders and try to figure out what you think the company is currently worth to you, if you were the sole owner. if there's basically no chance that the company can become profitable without taking a large amount of new investment then arguably the value of the company it its current form as a going concern is zero, although it may have some small value if the company were liquidated immediately and any residual cash left after paying off creditors was distributed to shareholders.

if your rough valuation of the current value of the entire company is less than $590k = 20 * 679 / 0.023 [1] then the intrinsic value of your options is $0 and the remaining time value of the options is rapidly approaching $0 if you are nearing the end of the 90 day exercise window. This is fine, it just means that the financial instrument you currently own, these options, are currently almost worthless and are likely to become completely worthless in the very near future [2]. There are plenty of other far less speculative ways to invest that have a far better chance of giving you a modest return on investment and not destroying your capital.

another angle: let's assume the current value of each option is approximately $0 and ignore them. if you are open to the possibility of investing some of your capital into this startup, instead of becoming a shareholder, would it be a better idea to instead become a creditor? e.g. supposing you had $20k cash you were open to investing, do you think the company would agree to terms where they get your $20k and you become a bondholder with a bond entitling you to e.g. 20% dividend payment per year for n years then full return of your initial $20k capital, and status as a secured creditor with the first claim to any remaining assets when the company goes bankrupt? Supposing the company were having a fire-sale of its assets, how much would you pay for the IP (or the desks or other physical assets with resale value...) [3]

yet another angle: on an unrelated note, you say you already hold the company's digital currency. how much is this currently worth in USD? if it is worth > $0 USD, can you sell this digital currency in exchange for cash? failing that, can you sell this digital currency back to the company to cover the cost of exercising the options?

[1] this assumes each option is for 1 share in the company not 100 shares in the company, as would be the case for options typically traded on the market ... if the latter case is true it would cost $20 * 100 * 679 = $1.36 million to exercise the options, and would only make sense if you valued the company as currently being worth more than $590m

[2] worthless in an optimistic scenario where you refrain from exercising the options. if you exercise when the strike price is above the value of the underlying share, you destroy the time value (maybe slightly more than zero), and take the immediate loss for trading $20 cash for a share worth less than $20.

[3] this is almost certainly not a sensible scenario but thinking about it provides quite a different perspective. If you are willing to invest, is there some way to structure the investment so you win or don't lose too much in the high-probability scenario where the company goes bust?