Looking for ideas to spend one year or more in Japan

Hi, as the title implies, I'm hoping to spend one year or more in Japan. I live close by and travel there semi-frequently. Here are some pointers to help you help me:

1. I'm a Master degree holder and have worked as an ESL teacher abroad for many years, though I do not see myself as an ALT in Japan.

2. I'm open to Ph.D. opportunities, but I'm too old for MEXT and too poor for self-funding.

3. I considered a hybrid approach between the Digital Nomad visa and tourist visas (3 months before and 3 months after) although I'm not sure if it's okay to do this, plus I do not like the idea that you are not counted as a resident with a DN visa.

4. I considered software engineering roles. However, my skill level is intermediate, and my Japanese level is N4'ish, so I doubt I can find visa-sponsored work with this configuration.

P.S. I don't mind spending 6 months to 1 year preparing for this. I just want to prepare for the right path.

Thanks.