You should start with the developing of the product as is happens, then use Continuous Improvement process to improve the development process.
You can use SCRUM/Kanban/SaFE/LeSS, hybrid or other Agile methodology, or no process at all, but it will not help when people are not trained to be proper part of the process.
For example, a PM may replace SCRUM meeting with a status meeting, because it makes his job easier, while PM or other M should not attend a SCRUM meeting at all, unless called in by engineers. The proper moment for interaction between PM and engineer are beginning/end of a ticket, sprint review, and sprint planning.
You can use SCRUM/Kanban/SaFE/LeSS, hybrid or other Agile methodology, or no process at all, but it will not help when people are not trained to be proper part of the process.
For example, a PM may replace SCRUM meeting with a status meeting, because it makes his job easier, while PM or other M should not attend a SCRUM meeting at all, unless called in by engineers. The proper moment for interaction between PM and engineer are beginning/end of a ticket, sprint review, and sprint planning.