In addition to Carta (which has a sentiment of being overpriced), there's also https://pulley.com [1], and LTSE Equity [2] [3] (formerly Captable.io). And spreadsheets.

[1]: https://pulley.com/compare/pulley-vs-carta & https://carta.com/carta-vs-pulley/

[2]: https://equity.ltse.com

[3]: https://carta.com/carta-vs-captable-io/