This subject is one of great interest to those of us with lung diseases for which there is currently no known cure. The paper you cited ( https://pubmed.ncbi.nlm.nih.gov/29344809/ ) is from a study 7-8 years ago, so I dove into Google Scholar to see if there is any news of note.

Here is article from 2023:
https://link.springer.com/article/10.1186/s12967-023-04729-9
The current limitation is a familiar one - HOW to manufacture these unique stem cells in sufficient quantity and purity that they are a practical solution for thousands to millions of people. That breakthrough has not yet been achieved, so any treatments now will be in a research setting like in the study cited above, or as last-resort care for those who are at the end of life and for whom lung transplant is not as possibility.

This is part of their conclusion: " To date, most of the research on the treatment of chronic lung diseases with engineered MSC-exos has been in the basic experimental stage. As an emerging treatment strategy, its safety, effectiveness, and feasibility still need further evaluation, and so high-stage clinical trials are urgently needed. In addition, since engineered MSC-exos can obtain different therapeutic characteristics through different engineering methods, their heterogeneity in different patients can result in good targeting adaptability, providing new ideas for the individualized treatment of chronic pulmonary diseases. Although engineered stem cells are an emerging treatment strategy and require further research and clinical trials, their enormous potential does suggest the possibility for conquering difficult-to-treat pulmonary diseases."

If you want to dig into where there might be clinical trials, use this link:
https://clinicaltrials.gov/expert-search
In the search box type [mesenchymal stem cells] space [lungs] (or pulmonary or bronchiectasis) to see what is ongoing, or possibly recruiting. If they are recruiting there will be contact instructions. I cannot vouch for completeness or update on the list - often when a researcher leaves a team, the ball gets dropped and no more info is added.
Those of us who are "research nerds" periodically keep an eye on this and other research, so watch for more info.