Jira has some merits, but its most common uses are for companies in which the priority is to look busy (e.g., growth startups, inefficient established companies).
For early startups that can't rely upon VC-growth appearances and shotgun-approach hiring alone, I propose a complete selection of tools, including a substitute for Jira:
1. Get GitLab. Maybe hosted initially, but eventually self-hosted if you stay in business long enough.
(a) Do code in GitLab Git. Eventually including mirroring and auditing third-party dependencies (but your first few months of prototyping you'll probably be playing third-party package system roulette, and maybe even piping curl into bash from random offshore file-sharing sites run from countries without extradition treaties).
(b) Do project management and issue-tracking in GitLab Issues, with the Boards and the structured tags, for something Kanban-ish. (And someday someone will make great integrated Gantt.)
(c) Do engineering docs in Markdown files in (GitLab) Git when you want the docs versioned alongside the code. Whether it's embedded API docs/comments, or standalone Markdown documents.
(d) Do all remaining internal documentation in the crappy-looking GitLab Wiki. Emphasize low-friction, teach people how wikis are supposed to be used, and make this this canonical go-to from which all other information can be found (including those engineering docs that are in with the code). Even notes on nearby restaurants and nostalgia can go into the wiki -- you're an early startup, enjoy the efficiency and flatness and coolness while you can. Discourage anything that looks like siloing, fiefdom, staleness, BS, etc. It goes into the wiki unless it should be branched&versioned with code.
2. Tell everyone: Everything Goes Into GitLab.
3. Unfortunately, you also need videoconf and text chat. Useful non-ephemeral data from these gets captured in GitLab, probably into the Wiki. (For example. wiki page "2024-02-14 Cat Affordances Meeting", which started in advance of the meeting with an "Agenda" section. Then, during the meeting, was put up on the screen and had a "Notes" section quickly appended. Saved, done, linkable, findable, unpolished, sufficient.)
4. Don't add more docs&comms tools/SaaSes until someone can say why it can't just go into GitLab. Don't even spend time looking into this unless you're actually feeling pain from "Everything goes into GitLab".
5. If someone ignores the rules and starts putting company data into some random other SaaS (like "digital consumer natives" tend to do), have a thoughtful talk with them about Everything Goes Into GitLab and how they feel about that. While in parallel another employee deletes the SaaS account with extreme prejudice, blocks the SaaS in the company firewall, and posts a picture of the SaaS's head on a stake in the startup's kitchenette as a warning to other SaaSes.
6. If the startup is successful, there will be plenty of time for some Vice President of Procurement, who has little idea how people work, much less how they could be working effectively, to be wined&dined by an enterprise sales representatives, and to buy loads of enterprise licenses of Ass-sauna, Jeers-a, Effluence, BS Screams, etc. Only then will you realize how good you had it before, with your early startup, and you didn't appreciate it nearly enough. You will suffer until a vesting milestone, consult with your tax accountant, and then make your escape. To do your own early startup, where the first thing you do will be to proclaim: Everything Goes Into GitLab