SQL upgrade fails on 5.14.2 to 5.15.0 on Joomla
I see from your video that you're failing on the 5.15.alpha1 SQL, and on.

The first one has two SQL statements.  Essentially, the statuses for a contribution ("Pending", "Complete", etc.) and for recurring contributions have been the same - but moving forward they'll each have their own list.  The two SQL statements create an option group along with values to support this.

Run this SQL: select id, name from civicrm_option_group WHERE name = 'contribution_recur_status';

You should get back one result.  If you have no results, that's a problem:

+-----+---------------------------+
| id  | name                      |
+-----+---------------------------+
| 138 | contribution_recur_status |
+-----+---------------------------+


Then run this SQL: select cov.id, cov.option_group_id, cov.name, cov.label, cov.value from civicrm_option_value cov JOIN civicrm_option_group cog ON cov.option_group_id = cog.id WHERE cog.name = 'contribution_recur_status';

You should get back some number of results - I get 12, you may have more:

+------+-----------------+----------------+----------------+-------+
| id   | option_group_id | name           | label          | value |
+------+-----------------+----------------+----------------+-------+
| 1884 |             138 | Completed      | Completed      | 1     |
| 1885 |             138 | Pending        | Pending        | 2     |
| 1886 |             138 | Cancelled      | Cancelled      | 3     |
| 1887 |             138 | Failed         | Failed         | 4     |
| 1888 |             138 | In Progress    | In Progress    | 5     |
| 1889 |             138 | Overdue        | Overdue        | 6     |
| 1890 |             138 | Refunded       | Refunded       | 7     |
| 1891 |             138 | Partially paid | Partially paid | 8     |
| 1892 |             138 | Pending refund | Pending refund | 9     |
| 1893 |             138 | Chargeback     | Chargeback     | 10    |
| 1899 |             138 | Processing     | Processing     | 11    |
| 1900 |             138 | Failing        | Failing        | 12    |
+------+-----------------+----------------+----------------+-------+


You're also failing on "Fix cache key column name in prev next cache". 
That's trying to run this SQL, so also run this command manually:
ALTER TABLE civicrm_prevnext_cache CHANGE COLUMN  cacheKey cachekey VARCHAR(255) COMMENT 'Unique path name for cache element of the searched item';